Docker - Spring Boot application - cannot access MySql server on localhost

Question

How can I connect a Spring Boot (JAR) application, running in Docker, to my MySql server on my computer? [I tried different posts, but that didn't help]

In my Spring Boot 'application.properties' I have:

spring.datasource.url = jdbc:mysql://localhost:3306/geosoldatabase

I tried a number of options:

$ docker run -p 8080:8080 --name containername imagename

$ docker run --net="host" -p 8080:8080 --name containername imagename

$ docker run -p 8080:8080 --add-host=localhost:192.168.99.100 --name containername imagename

But alas, I cannot get connection to the MySql server. Hibernate fails. On my CAAS provider this all works nicely - of course with a known container name.

My Dockerfile is very simple:

FROM fabric8/java-jboss-openjdk8-jdk
ENV JAVA_APP_JAR myapplication.jar
ENV AB_OFF true
EXPOSE 8080
ADD target/$JAVA_APP_JAR /deployments/

As suggested, environment variables can also be used. This is what I've done so far:

• Define in Windows10 environment settings screen, I define the following environment variables: [1] DATABASE_HOST=127.0.0.1:3306 and [2] DATABASE_NAME=mydbname
• I changed the application.properties file as suggested: spring.datasource.url = jdbc:mysql://${DATABASE_HOST}/${DATABASE_NAME}

In the Docker Quickstart screen after I type "docker push... " I get the same errors. This time the cause is different:

Caused by: java.net.UnknownHostException: ${DATABASE_HOST}: Name or service not known.

To check whether the environment variables are correctly set, I type: "echo ${DATABASE_HOST}" and I get the value "127.0.0.1:3306".

Update: suggested was to put the 'docker-machine ip' address into the database_host variable. The cause was now a bit different:

Caused by: org.hibernate.tool.schema.spi.SchemaManagementException: Unable to open JDBC connection for schema management target

Answer 1

Use --network="host" in your docker run command, then 127.0.0.1 in your docker container will point to your docker host. Refer to the answers in this post.

Answer 2

Alright so, as promised - I just tried this myself.

Assuming your localhost mysql instance is running on the default port 3306, have the following in your spring boot project's application.properties:

spring.datasource.url = jdbc:mysql://${DATABASE_HOST}/${DATABASE_NAME}

and then run your spring boot app in the docker container with the following environment variables

DATABASE_HOST=127.0.0.1:3306
DATABASE_NAME=yourDBname

Do not add the port in the properties anywhere if you use the above config. Alternatively for testing shove these directly into the spring.datasource.url in the application.properties

Good luck.

Answer 3

You need to have an environment variable in the Spring boot application properties in place of "localhost" in the mysql URL. Set it to be localhost as default:

MYSQL_HOST=localhost
spring.datasource.url = jdbc:mysql://${MYSQL_HOST}:3306/geosoldatabase

Then you can pass the MYSQL_HOST environment variable as part of the docker run command. It should be the name of your mysql container. So give it a specific container name like "mysql"

A better way is to use docker compose and specify a network in the compose file and pass the environment variable in in the same way as above. Hope that helps.